Dumbell



FIG. 1 is a front perspective view of a dumbell showing my new design;

FIG. 2 is a front elevational view thereof, the side opposite being a mirror image;

FIG. 3 is a top plan view thereof;

FIG. 4 is a right side elevational view thereof, the side opposite being a mirror image thereof; and,

FIG. 5 is a bottom plan view thereof. 

The ornamental design for a dumbell, as shown and described. 